Conventional catheterizations controlled by fluoroscopy are generally performed in hospitals, require complex X-ray equipment installed in a particular hospital facility such as a catheterization laboratory or radiology department and must be carried out by specially qualified physicians trained in catheterization procedures—Consequently, these conditions cannot be met in emergencies when the equipment and trained personnel required for catheterization are not readily available.
However, in many cases where there is an urgent need for catheterization, the rapid transfer of severely ill patients to a suitably equipped location can be quite problematic and may entail serious risks, even in the case of in-hospital interventions. The transfer of a patient to the next suitably equipped hospital usually takes some time and could affect the patients chances of survival.
The U.S. Pat. No. 5,391,199, U.S. Pat. No. 6,246,898 and the patent publication WO9945994 may illustrate the prior art relating to conventional catheterization using fluoroscopy imaging to show the progress of a catheter through a patient's body.
A system for externally locating a catheter described in U.S. Pat. No. 4,173,228, U.S. Pat. No. 5,425,367 and U.S. Pat. No. 5,645,065 comprises an external probe for locating a catheter tip having an inductive coil for delivering an induced signal in response to a rotating magnetic field generated by the external probe.
However, in the majority of situations requiring catheterization, the heart's structures are the main targets of interest for intervention and they constitute moving targets with variable coordinates, which can only be determined with a limited degree of accuracy.
Externally positioned 3-D sensors do not allow the intravascular position of the catheter to be ascertained and some degree of control by fluoroscopy is nevertheless necessary.